Conventionally, an image pickup apparatuses provided with a zoom mechanism is presented.
For example, in an endoscope field, such an image pickup apparatus is provided in an endoscope system. In this case, a zoom mechanism and the like of the image pickup apparatus are provided within a small space called a tip portion of an endoscope in the endoscope system. Accordingly, an image pickup apparatus provided in the endoscope system sometimes includes, as a zoom mechanism, a zoom mechanism using a VCM (Voice Coil Motor) that is advantageous for downsizing. With such a zoom mechanism, the VCM moves a zoom lens so that an optical image formed on an imaging surface is enlarged or reduced.
As other image pickup apparatuses that are included in an endoscope system and have a zoom mechanism, image pickup apparatuses that are disclosed, for example, by Japanese Laid-open Patent Publication No. 2011-98051, Japanese Laid-open Patent Publication No. 2010-282073 and Japanese Laid-open Patent Publication No. 2011-15883, and that include a zoom mechanism are known.
In the above described image pickup apparatus having the zoom mechanism using the VCM, the position of the zoom lens is not fixedly retained by the VCM. Therefore, a feedback control (servo control) for detecting the position of the zoom lens and for moving the zoom lens to a target position on the basis of a result of the detection is always performed. Here, the position of the zoom lens is detected by a position detection mechanism. Similarly to the zoom mechanism, the position detection mechanism is provided within a small space called a tip portion of an endoscope. Therefore, a position detection mechanism of a small size is used.